Process of removing germanium from zinc sulphate solutions



Patented Mar. 8, 1932,.

PATENT .Q FF

' m DE N I'rCIIEnLJOF GREAT MONTANA, ASSIGNOR T0 ANAcoNnAcorrnn TMINING COMPANY, A CORPORATION or. MoNTANA A i noo zz'ssoFfREMoVINGGERMANItMFROM zINc SULPHATE soLU'rioNs i l'ates to'thesubstantially complete removal of; -ge'rmanium i from -z1 ncsulphate solutions andpa'rticul-arly from so 'lutionstha-tare tofbe subjectedto electrolysis;

which. is; thereby'largely, but not completely,

for recovery of zinc;

electrolysiS QI'cuSualIy, obtained by leaching roa ted, in ores, fumes or other basic zinc ompound u na lyfca1 d'zfin c lcineg th dilute sulphuric acjid which is usually-ob tained in the electrolysis: of a preceding quantity ;:oi:' 1 zinc sulphate, Zinc calcines 1 that are availableafor this: treatment com- I monl contain other metals'or com ounds ofthesemetals}v as impurities. To prev vent {the dissolutiohiof such impurities and 1 V to i remove; themliias much, as ;:possible the} .Ca-lGlDeriS leached i'n'two stages, in the {sec v 0nd (bf-which it is, treated directlyywithanexcess of faciid iirom the electrolytic tanks neutnalizedl fTh-is partlyzneutralized fiCldlS ing zinc "sulphate solution ;-containing;the remainingimpurities" must, therefore, be treated with other reagents and finally with zinc dust to remove these remaining. impurities before the solution is subjected to electrolysis; Germanium istone of'gth'eimpuritie's contained" :in ;-raw calcine. It is present; in: zinc concentrates in amounts varying from .001%, whichis the lowerassaylli-mit,to .930%. It

is alsofpresent ingcertain zinc oxide, fumes which it occurs in amounts varying; from 030% to .'IOO%. [Certain fumes-from lead, smelters havealso been to ,contain ger-H mani'um} Germanium, is a serious impurity when it 'isp'resentin' concentrates, calcines or er janetallurgical. products 1m amounts r'jt'hani001%.".

1 iieation filed may 10,

1930. 'seria1No.451,524.

as in the steps mentioned above, the first or this leach, usually having amaximumfof 3.0%, and because theleach itself actsj'as a1 'partia1 purification; Some germanium is,

however. dissolved in succeeding leaching steps.

I When the calcine is subjected to leaching 4 The leach solution: from these acid". leaches are mixed w-iththe neutral leachfor partial; purification. This is an oxidizing purification in an acid solution which issubs sequently neutralized with a large excessf'of zinc oxide calcine.

The zinc sulphate solutions must be puris fie'd before electrolysis to remove metals such as cadmium which are deposited with zinc and lower the grade of metalthus produced, and

to remove impurities such as copper, arsenic,

antimony, cobalt and germanium, which.

would prevent zinc from being deposited. These impurities are removed bytreating the solutions withran excess of zinc dust, blue powder or other finely divided metallic zinc which, being more electropositive than the metals constituting the impurities, displaces the latter from the solution.- Inorder to in sure a suficientremoval of the impuritiesa considerable excess of zinc dust is required. The germanium remaining in the solution after the neutral leach must be removed in the next and last treatment of the solutionprior to electrolysis which is the aforesaid purifica tion Withzinc dust. r A

The etl'ect of germanium on theelectrolysis of zinc sulphate solutions is to lower the hydrogen overvoltage of the zinc, thereby caus ing the zinc "to re oxidize and re-dissolve.- This efiect is even more' apparent in the zinc dust purification 'wh'er'e'the germaniumcauses the oxidation ofboth the excess zincdust pres ent and the precipitated cadmium. Th eseiav o oxides {then react with zinc sulphate with the i 7 formation of basic zinc sulphate and cadmium sulphate. These reactions are represented as follows (1) Zn(meta1) H20 (Ge) cata1yst=ZnO H2 (Ge) (2) ZnO 'znso, n o=z'ng ori gso.

(1 and 2) Zn(metal) 2H O ZnSO (Ge) Zn (OH) SO H: (Ge) (3) Cd(meta1) H2O Ge(catalyst) =Cdo H: (Ge) (4 CdO znso.=zno case. (5 ZnO znso. n o=zn oH so.

(3 and 4 and 5) Cd(meta1) 2H20 2ZuSO (Ge) I zn oH) so.+caso.+r1 (Gel Being catalytic reactions, relatively small amounts of germanium cause the precipitated cadmium to re-dissolve very rapidly and seriously reduce the amount of excess zinc dustpresent. For example, zinc sulphate solutions similar to that obtained by leaching were made up from chemically pure reagents to contain 45 grams of zinc, .05 grams of iron and,5.0 grams of manganese per liter. One of these solutions was electrolyzed directly and others were electrolyzed after the addition of varying small amounts of germanium sulphate. It wasfound that the presence of germanium to the extentof .0005 grams per liter reduced the ampere efficiency from 93.3% to 81.0%. \Vhen the quantity of germanium was .0010 grams per liter, the ampere'efiiciency fell to 72.5%. In similar solutions containing .005 grams of cobalt per. liter thepresence of .0005 grams of germanium per liter reduced the ampere efficiency from 92.8% to 71.6% and when germanium was present to i the extent of .0010 grams per liter in such a v cobalt-containing solution'no zinc metal was obtained after electrolyzing for twenty four hours.

I As pointed out above, the presence of ger- 40 manium also prevents the removal ofother, impurities such as cadmium. For example,a

solution containing 100 grams of zinc, .9 grams of copper, .25 grams of cadmium and .006 grams of cobalt per liter was treated with zinc dust, the quantity of cadmium per liter was reduced in one-halfhour to .001 grams, this quantity rising to .004: grains after treatment for four hours. A similar solution containing in addition .0025 grams per liter of germanium when treated with zinc dust contained after one-half hour of treatment .010 grams of cadmium per liter which quantity rose after one hours treatment to; .089, then after two hours treatment to .18-

1 and with four hours treatment to .25 grams per liter, the entire quantity of cadmiumoriginally present. The object of my invention is therefore to remove the germanium from zinc sulphate and similar solutions and to:

reduce the'quantity of germanium remaining in such, solutions to a point below that at which it has a deleterious action on the purification and electrolysis of the solution. i

When the calcine contains up to .001% of germanium, the germanium may be removed by agitating the leach liquor from two to three hours with 2.5 to 3.0 grams per liter of zinc dust. This treatment produces a purification residue assaying .010% to 020% of germanium. This treatment is, however, not applicable to solutions derived from a concentrate feed containing more than .001%.

A further object of the invention is therefore to remove ermanium from solutions obtained by treating concentrates containing more than .001% of germanium.

In the present invention, the solution to be purified is agitated in a tank with purifying agents for a period of from two to five hours depending upon the amount of germanium to be removed and the temperature. The higher the temperature, the better is the purification. The solution may be heated if desirable. When the germanium content in the solution hasbeen displaced, the solution is filtered from the residue which contains the germanium and this solution is sent to the electrolyzing cells. The reagents employed in the above outlined purification process may be a zinc or-calcium oxide, hydroxide, or carbonate, or the oxide, hydroxide or carbonate of'any'metal more basic than zinc. Or zinc dust maybe employed with or without an addition of copper sulphate, and with or without an addition of the oxide, hydroxide or carbonate of zinc, calcium or of any other metal more basic than zinc; or with the addition or substitution of a solution of cadmium sulphate orof arsenic trioxide in place of the copper sulphate. v

As an example of a purification of a zinc sulphate solution containing germanium, a quantity of copper'sulphate is added to the leach solution to be purified, until the solution assays .7 to 1.0 grams of copper per liter. 3150 20 grams per liter zinc dust is then added to the solution, the quantity of zinc dust depending upon'the germanium content of the solution. The solution is then filtered giving a filtrate containing 100 grams per liter of zinc and from only a trace to .010 grams per liter germanium, and a purification residue assaying approximately 40% zinc, 10% copper and from .010 to .30% germanium. Copper may be added to the solution as metallic copper or by addingcopper sulphate to the leach solution or to the material to be leached or by adding roasted copper bearing ores to the material to be "leached or by adding uni roasted copper bearing ores to the zinc concentrate prior tocalcining or roasting win any other suitable'and convenient manner.

The above method may be modified by adding 1 to5grams of zinc oxide per liter to the solutiorito be purified, or by adding calcium oxide, or calcium carbonate, or the oxide, hydroxide, "or carbonate of any metal more basicthan zinc, thereupon treating the mate'- rial as above i "Instead of using copper, cadmium sulphate may be added to the solution to be purified until the latter contains .1 to .3 grams of cadmium per'liter or .1 to .3'grams of cadmium as cadmium sulphate may be added to each liter of the 'solution'in addition tothe increase. incopper content of from .1 to 1.0 grams per liter. The cadmium may be added as cadmium sulphate to the leach solution or to the material. to be leached or by adding to the concentrate before roasting, purification residue, or the cadmium sponge recovered; ,from purificatlon resldue as, described, in

United States PatentNo. 1,343,619. Or these materials may be oxidized and added to the calcine to be leached. Arsenic trioxide may be added to the solution in addition to the copper and zinc dust until the solution assa 5 from .1 to 1.0 grams per liter arsenic. nstead of'using zinc dust the solution may be purified bv precipitating the germanium with zinc or calcium oxide, hydroxide or carbonate, or the oxide, hydroxide, or carbonate of any metal more basic than zinc. In

"thls process no zinc dust, copper sulphateor cadmium sulphate need be added to the solu-;

from to tion. vTreatment'with oxides of the abovev type requires a longer time and higher tem- 'peratures 7 than treatment v with zinc dust.

The residue from this latter process assays ofzinc' and .010 to 30%, of germanium.

In the event that the concentrate or calcine contains too high a germanium content for the usual treatment-and provided that it may be separated into a portion sutficiently f lowin germanium for direct treatment with zinc dust and .into another portion of high germanium content, the high germanium containing portion may be treated separately by germanium contents thereof, treating the second portion with a basic compound of a metal not less basic than zinc, filtering the any of the above methods, and the purified I solution thus obtained may be mixed with i the leach solution from the portion of low germanium content, which -may then be treated with zinc dust. In this way, the leach solution from the material of high germanium content is given a double purification.

- This method is particularly desirable in treating fumes'of high germanium content. The

- leach solution from such material may assay from .010 to .100 grams per liter ofgermanium and a double purification is almost essentialto obtain: a solution sufiiciently pure for efl'ec'tiveelectrolysis. To obtain good results for electrolysis, the germanium content should not be over about .0002 grams of germanium per liter.

lVhat I claim is The method of treating zinc sulphate solutions containing a high germanium content in order to render them suitable for electro lytic extraction of zinc, which method consists in separating the solution into a first 1 portion comparatively low in germanium and a second portion comparatively high in germanium, treating the first portion of the s0lution directly with zinc dust to reduce the, 

